One of Thailand’s leading hospitals, known for treating medical tourists, said on Friday it had received the country’s first case of Middle East Respiratory Syndrome (MERS), as authorities said it had taken nearly four days to confirm the illness.

Thailand said on Thursday a 75-year-old businessman from Oman, who had traveled to Bangkok for medical treatment for a heart condition, had tested positive for MERS.

The announcement came just as an outbreak in South Korea that began last month and has infected 166 people, killing 24 of them, appeared to be leveling off.

The high-end Bumrungrad Hospital, run by Thailand’s second-largest hospital operator, identified the first MERS case. The hospital in central Bangkok treats over a million patients a year, about half of them foreigners.

“The patient came to us tired, coughing … there was no fever,” a doctor from the private hospital told a televised news conference. “So we X-rayed his chest … we found that he could have two things, a heart condition or the MERS virus.”

Tourism accounts for 10 percent of the Thai economy and medical tourists make up more than 10 percent of visitors, according to the Tourism Authority of Thailand. About a third of those medical tourists come from the Middle East.

The hospital said 58 staff had been quarantined, but all other operations were continuing as normal.

The infected man was moved to Bangkok’s Bamrasnaradura Infectious Diseases Institute on Thursday. Staff there were seen wearing and giving out masks to visitors, according to a Reuters reporter at the scene. Health warnings were posted in front of the building’s entrance.

Two South Korean hospitals were locked down and another completely shut due to MERS, while the prestigious Samsung Medical Center in Seoul, where most infections occurred, stopped taking new patients during the outbreak.

The Thai case will compound fears in Asia of a repeat of a 2002-2003 outbreak of Severe Acute Respiratory Syndrome (SARS), which began in China and killed about 800 people globally.

MERS was first identified in humans in Saudi Arabia in 2012 and the majority of cases have been in the Middle East.

Isolated cases have cropped up in Asia before South Korea’s outbreak began last month, and Thailand is the fourth Asian country to register a case.

China has had one case recently, that of a South Korean man who traveled to China via Hong Kong despite authorities suggesting he stay in voluntary quarantine at home. The Philippines has also identified a case this year.